X-linked myotubular myopathy (XLMTM)
This is one of the more common types of CNM and the most severe. Due to its specific inheritance pattern the condition almost always affects boys. At birth, the symptoms include hypotonia (floppiness), breathing and swallowing difficulties. Motor skills are the most affected, causing difficulties with sitting, standing and walking. The muscles controlling eye movements are almost always affected, but problems with eye movement may not begin until later in life. Some people may need to use a ventilator to breathe. Difficulties with feeding often result in the need for a feeding tube inserted into the stomach. Sadly this condition may mean a reduced life-expectancy for the child, mainly depending on the degree of breathing difficulties.
Autosomal recessive CMN (ar-CNM)
ar-CNM usually occurs in infancy or early childhood. Symptoms include hypotonia, breathing and swallowing difficulties. There is usually weakness of the muscles closest to the trunk of the body, known as the proximal muscles. Weakness of the face muscles may occur, including droopiness of the eyelids and abnormalities of eye movements. Some children may have problems with feeding, and may require breathing support.
Autosomal dominant CNM (ad-CNM)
ad-CNM is generally not as severe as the X-linked or the autosomal-recessive forms. Symptoms develop slowly from birth until well into adulthood. Many affected people are able to walk well into adulthood, but may find themselves in a wheelchair in later life.